Climate change, with extreme phenomena such as droughts and torrential rains, added to the abandonment of forest management and changes in land use, can produce fires of great magnitude against which firefighters can hardly do anything.
These are known as “sixth generation” fires and are often devastating. They have been observed in Australia, the United States and now in southern Europe, where an intense heat wave fuels veritable fire monsters.
Phenomena of the type, such as the one that killed more than 60 people in Portugal in 2017, are becoming more frequent.
Danger
These are very dangerous fires, which seem to take on a life of their own and have an ability to withstand the work of firefighters.
The intensity of the fire prevents the teams from getting closer, all that remains is to hope that it starts to rain.
The concept of “generation” applied to fires has to do with how fire behaves in the terrain where it occurs.
In the case of the “sixth generation”, the energy they release is such that they have the ability to change the climate around them and even generate new outbreaks.
“It is known that climatic conditions can increase the risk of fires and make them more difficult to extinguish. But the relationship between fire and climate goes further. Fires can create their own climate, generating pyrocumulonimbus clouds and storms”, he explains in his website the government weather service of Australia, a country that has faced some of these devastating fires.
What are pyrocumulonimbus clouds?
They are, literally, electrical storms that form on top of the smoke column of a fire, but they can also be created in the ash clouds of volcanoes or in the mushrooms of a nuclear detonation.
How are they formed?
The intense heat of the fire causes the air to rise rapidly with a column of smoke. This hot air is very turbulent and cools as it rises. The higher it is, the lower the atmospheric pressure, which causes this column to spread out and continue to cool.
If the temperature drops enough, the moisture in the column condenses and forms a cumulus, a cloud. But as it was formed by fire, this cloud is called “pyrocumulus”. The condensation process causes this latent heat to be released, so the cloud heats up and rises even higher.
This cloud can reach the lower stratosphere without losing buoyancy. The collision of ice particles in the upper parts of these clouds can create electrical charges that release huge sparks and lightning. These types of clouds that can cause thunderstorms are called pyrocumulonimbus.
These clouds can produce very destructive torrential rains. The lightning, moreover, is capable of causing new outbreaks of fire. They are therefore known as “fire storms”.
Why are they produced?
The “sixth generation” fires are one of the clearest consequences of the climate emergency. As with the oven, climate change has “preheated” the environment and created the right conditions for this type of fire to exist.
The increase in temperatures has caused some plant species to appear in areas for which they are not adapted. In addition, the rains are increasingly short and intense and cause flooding, soil loss and problems with water absorption.
What are the previous five generations?
Fires have evolved since, in the mid-20th century, a rural exodus took place in many parts of the world, and agricultural areas were abandoned.
First generation: fires spread in agricultural areas that were no longer being used.
Second generation: the vegetation starts to recolonize old abandoned farms, but this new forest mass is abandoned. With these fires, it is observed that there is a growing mass of continuous vegetation through which the fire can spread rapidly. Then came the first measures against fires: building firebreaks, a stretch of clean land to prevent the spread of fire.
Third generation: a dichotomy of the landscape emerges. The population is concentrated in the metropolitan areas while the countryside is emptied. This causes fires to gain intensity and consume the entire forest mass in which they start.
Fourth generation: In the 1990s, there was a boom of people acquiring second homes in rural areas in countries like Spain. These are urbanizations in the middle of the forest or countryside where people who do not make agricultural use of the countryside live. They are very voracious and dangerous fires.
Fifth generation: occur when there are several fires at the same time, causing the collapse of services.
And from there you get to the sixth generation, in which climate change created the right conditions to set off fires that were impossible to fight. You can only adopt a defensive strategy, that is, establish priorities and decide what you want to save.
The only way to combat it, experts say, is prevention.
Text originally published here.
